Semiconductor device

Abstract

The present invention relates to a structure of a capacitor, in particular using niobium pentoxide, of a semiconductor capacitor memory device. Since niobium pentoxide has a low crystallization temperature of 600° C. or less, niobium pentoxide can suppress the oxidation of a bottom electrode and a barrier metal by heat treatment. However, according to heat treatment at low temperature, carbon incorporated from CVD sources into the film is not easily oxidized or removed. Therefore, a problem that leakage current increases arises. As an insulator film of a capacitor, a layered film composed of a niobium pentoxide film and a tantalum pentoxide film, or a layered film composed of niobium pentoxide films is used. By the use of the niobium pentoxide film, the dielectric constant of the capacitor can be made high and the crystallization temperature can be made low. By multiple-stage formation of the dielectric film, leakage current can be decreased.

What is claimed is:  
     
       1. A semiconductor device comprising a capacitor comprising a first electrode, a dielectric film, and a second electrode, 
       wherein the dielectric film comprises a multiple layer film composed of a first film made of any one of a niobium pentoxide film and a film made of a composition of tantalum pentoxide and niobium pentoxide, and a second film made of any one of a tantalum pentoxide film, a niobium pentoxide film, and a composition of tantalum pentoxide and niobium pentoxide, and the first film is present on the side of the first electrode, wherein a crystalline grain boundary between said first film and said second film is separated at an interface of said first and second film.  
     
     
       2. The semiconductor device according to  claim 1 , wherein the first film is a film which is formed over the first electrode and has a first crystalline grain boundary and the second film is a film which is formed over the first film and has a second crystalline grain boundary separated from said first crystalline grain boundary at said interface. 
     
     
       3. The semiconductor device according to  claim 2 , wherein any one of the first and second films which constitute the dielectric film has a film thickness of 5 nm or less. 
     
     
       4. The semiconductor device according to  claim 1 , wherein the second electrode comprises titanium nitride. 
     
     
       5. The semiconductor device according to  claim 1 , wherein the first electrode comprises polycrystalline silicon. 
     
     
       6. The semiconductor device according to  claim 5 , wherein the composition ratio of tantalum to niobium in the first film is 40% or less by atom. 
     
     
       7. The semiconductor device according to  claim 5 , wherein rugged grains by silicon are made in the surface of the first electrode. 
     
     
       8. The semiconductor device according to  claim 1 , wherein the first electrode comprises any one selected from ruthenium, platinum, and copper. 
     
     
       9. The semiconductor device according to  claim 8 , wherein the composition ratio of tantalum to niobium in the first film is 90% or less by atom. 
     
     
       10. The semiconductor device according to  claim 1 , wherein the capacitor is a capacitor in which the first electrode comprising ruthenium is electrically connected to a plug comprising polycrystalline silicon through a barrier metal comprising any one selected from titanium nitride, titanium nitride to which aluminum is added, tantalum nitride, and tantalum nitride to which silicon is added. 
     
     
       11. The semiconductor device according to  claim 1 , which includes any one of a memory, a logic circuit, and an analog circuit. 
     
     
       12. A semiconductor device comprising a capacitor comprising a first electrode, a dielectric film, and a second electrode, 
       wherein the dielectric film comprises a multiple layer film composed of a first film made of a niobium pentoxide film, and a second film made of a tantalum pentoxide film formed over the first film, and the first film is present on the side of the first electrode, wherein a crystalline grain boundary between said first film and said second film is separated at an interface of said first and second film.  
     
     
       13. The semiconductor device according to  claim 12 , wherein the second electrode comprises titanium nitride. 
     
     
       14. The semiconductor device according to  claim 12 , wherein the first electrode comprises a material selected from a group consisting of ruthenium, platinum and copper. 
     
     
       15. A semiconductor device comprising a capacitor comprising a first electrode, a dielectric film, and a second electrode, 
       wherein the dielectric film comprises a multiple layer film composed of a first film made of a niobium pentoxide film, and a second film made of a niobium pentoxide film formed over the first film, and the first film is present on the side of the first electrode, wherein a crystalline grain boundary between said first film and said second film is separated at an interface of said first and second film.  
     
     
       16. The semiconductor device according to  claim 15 , wherein the second electrode comprises titanium nitride. 
     
     
       17. A semiconductor device comprising a capacitor comprising a first electrode, a dielectric film, and a second electrodes 
       wherein the dielectric film comprises a multiple layer film composed of a first film made of a composition of tantalum pentoxide and niobium pentoxide, and a second film made of a composition of tantalum pentoxide and niobium pentoxide formed over the first film, and the first film is present on the side of the first electrode, wherein a crystalline grain boundary between said first film and said second film is separated at an interface of said first and second film.  
     
     
       18. The semiconductor device according to  claim 17 , wherein the first film and the second film are made to have substantially the same composition ratio between tantalum pentoxide and niobium pentoxide.